Dump the bottled sauerkraut into a jar and let it drain well while you prep other ingredients.
Cut away the core from the head of cabbage, and separate the cabbage into cups. (You can cut the cabbage in half if you want smaller cups, but we kept them whole and trimmed the edges after we put in the filling.
Cut up one pound of leftover or deli corned beef into small pieces.
Chop up a small onion. Heat olive oil in a non-stick frying pan over medium=high heat and cook the onion a few minutes, until it's starting to brown.
Add the small pieces of corned beef and cook, turning several times, until it's heated through and starting to lightly brown.
Fill each cabbage cup with some of the heated corned beef. (We trimmed the edges of the cabbage cups with Kitchen Shears (affiliate link) to make them a more manageable size, but that is totally optional.
Put a few ounces of well-drained sauerkraut over the corned beef.
Then top with about 2 tablespoons of Thousand Island Dressing, or however much you prefer.
Serve with additional Thousand Island Dressing to add at the table and enjoy!
